HEXiT :
350w is enough to run the 7770 as it uses about 76w at full load and can get most of that from the the pci-e slot. as you have a 94gt already you should have enough power to run the 7770
The 9400GT requires less power than the 7770 (recommended is 300W vs 400W, so in reality 250W vs 350W), so being able to run it doesn't mean he can run the 7770. Also, the 7770 requires a PCI-E power cable, which most 350W cheap PSUs don't have.